Synthesis of Porous Silicon Nitride Ceramic with a Compositional Gradient

M. Knoll; Monika Willert-Porada

doi:10.4028/www.scientific.net/MSF.631-632.477

Paper Titles

Development of Compositional Gradient Simulation for Centrifugal Slurry-Pouring Methods
p.455

Preparation of Tungsten-Epoxy Composites and FGMs with Density Gradient
p.461

A Trial of FGM Bearings with Solid Lubricant
p.465

Interpenetrating Network Metal-Ceramic FGM – Preparation and Properties
p.471

Synthesis of Porous Silicon Nitride Ceramic with a Compositional Gradient
p.477

Crossover from Metallic to Semiconducting in Pb_2-xLn_xRu₂O_7-δ (Ln = Eu, Sm) Compounds with Pyrochlore Structure
p.483

Ca₃Co₂O₆ for High Temperature Side of Thermoelectric FGM
p.489

Evaluation of Lifetime of FGMs Disilicide Coatings for γ-TiAl Intermetallic Compound
p.495

Characterization of Manganese Oxide-Enriched Surface Layers of Fe-Mn Alloys
p.501

HomeMaterials Science ForumMaterials Science Forum Vols. 631-632Synthesis of Porous Silicon Nitride Ceramic with a...

Synthesis of Porous Silicon Nitride Ceramic with a Compositional Gradient

Abstract:

This paper summarises results of a study on graded surface layer composition in porous silicon nitride ceramics with a nominal Yb-silicate, Yb2SiO5-additive content of 3.2 mol%, corresponding to 10wt%. A compositional gradient of the additive is formed within the sintered part, depending upon the sintering conditions. The thickness and the phase content of the compositional gradient is significantly affected by the nitrogen activity of the sintering atmosphere. When argon gas is used during heating up and replaced by nitrogen upon soaking, the surface of the sintered ceramic is free of Yb2SiO5, whereas in N2-atmosphere a silicate-rich coating is found as surface layer of the porous silicon nitride ceramic. In presence of carbon and nitrogen, the surface is covered by SiC. In particular the Yb-silicate enriched surface layer can be used as base for an Environmental Barrier Coating, EBC, to protect the interior of the ceramic from hot gas corrosion.